DIY Passenger airbag switch

[martialmedia]

Here is a little tutorial that shows the construction and installation of a passenger side airbag deactivation switch that I built for my 2003 Bosxter S. Keep in mind that I am simply documenting a modification that I chose to make to my Boxster. I in no way encourage anyone to do the same. This mod has not been tested in an actual collision and is not approved by Porsche. If you choose to do this mod you do it at your own risk.

Now that all being said, I will start by directing you to this post which covers some aspects of this and shows a schematic that I used to create this box. http://www.renntech.org/forums/index.php?s...pic=9658&hl

The problem I had was that I don't have an infant, I have a 7 yr old. I don't need a child seat and I think the bar method is just sloppy. I don't know why Porsche didn't install a switch, so I did it for them. :)

This switch basically mimicks the output of the Porsche buckle system into a convenient switch. Essentially, when the switch is on, it puts 2.280K resistance which is the same as the bar being in the car without the buckle inserted. This tells the system that it has a device installed, but it is not in use. In this case, the computer keeps the airbag activated.

When the switch is off, it reduces the resistance to approx 255 ohms, which is the same as the bar being in the car with the buckle inserted. This tells the system that it has a device installed and that it is in use. In this case the computer deactivates the airbag.

Using the schematic, I built this box. There are 2 strings of resistance: One which totals 255 ohms and one that totals 2025 ohms. The switch bypasses the 2025ohm section.

Here is an image showing the electrical path when the switch is closed. When it's closed it allows the current to pass through and bypass the 2025ohm path.

Here is an image showing the electrical path when the switch is open. When the switch is open the current has to go through the 2025ohm section to exit, making the total resistance approx 2280ohms.

Here are the reading you should be getting out of the unit. This image shows the reading when the switch is in the "off" position which tells the system to turn off the airbag.

This image shows the reading when the switch is in the "on" position which tells the system to turn on the airbag.

I spliced a simple connector into the wire and behind the connector for the Porsche deactivation bar which is located under the passenger seat. This makes it tidy and easy to remove later if you choose.

Here it is installed.

A couple of notes:

1) The switch I chose allows you to connect it so that either "On" or "Off" can open or close the switch. This is important to watch and decide how you want to set it up. I choose to view it as an airbag de-activator, so I set it so that the switch in the "On" position actually sends the resistance to tell the computer to keep the airbag on which is the full 2280ohms. You could set it to the opposite if you wanted to view the switch as activating the de-activator. I hope that didn't get confusing.

2) Once installed, the switch will not turn off the airbag and the airbag warning light will come on until a dealer plugs into the computer with a PST2 to tell the system that a device exists. Once this is done, you should be able to flip the switch and the airbag warning light will flash for 60 secs to let you know that the airbag is deactivated. This switch will not work until it is enabled in the computer with a PST2. This is the same as the Porsche child restraint bar.

3) I plan to modify this so that I can run it to an actual Porsche switch in place of one of the blanks in the dash. I would like one with a red light to show that the airbag is off.

This is my first contribution, hopefully you will find it interesting at least. It only costs about $20.00 total and is very convenient. My dealer didn't charge me for the programming.

Edited November 21, 2009 by martialmedia

[demick]

I did basically the same thing on mine. Only I hooked up a switch to the center console compartment lock (had to remove the center console to do this). The lock still works as normal, but also now serves as an airbag disable. Lock the console compartment, and the passenger airbag gets disabled.

Now my kids (who are too big for a carseat and too small for an airbag equipped seat) can ride in the Boxster.

[martialmedia]

I did basically the same thing on mine. Only I hooked up a switch to the center console compartment lock (had to remove the center console to do this). The lock still works as normal, but also now serves as an airbag disable. Lock the console compartment, and the passenger airbag gets disabled.

Now my kids (who are too big for a carseat and too small for an airbag equipped seat) can ride in the Boxster.

Tell me more about this switch. How did you hook a switch to the compartment lock? That's an interesting idea.

Edited November 21, 2009 by martialmedia

[demick]

All of the electronics are still under the seat, same as yours. I just put a couple of resistors on a wiring board like yours, and shrunk wrapped the whole thing (only about 1/2" x 1"). A connector on one end connects to the connector under the seat. A pair of wires runs to the switch in the center console that when depressed, just bypasses one of the resistors under the seat. Attached is a picture of the lock inside of the center console. I made a metal bracket that fastens using the same screw that holds the lock in place. The switch is mounted to that bracket. As the lock is rotated into the locked position (shown), it depresses the switch. Green arrow shows how the lock rotates.

Edited November 21, 2009 by demick

[martialmedia]

All of the electronics are still under the seat, same as yours. I just put a couple of resistors on a wiring board like yours, and shrunk wrapped the whole thing (only about 1/2" x 1"). A connector on one end connects to the connector under the seat. A pair of wires runs to the switch in the center console that when depressed, just bypasses one of the resistors under the seat. Attached is a picture of the lock inside of the center console. I made a metal bracket that fastens using the same screw that holds the lock in place. The switch is mounted to that bracket. As the lock is rotated into the locked position (shown), it depresses the switch. Green arrow shows how the lock rotates.

Very clever. I like it. What was the resistance of the two resistors you used. I just used what Radio Shack had and had to chain them together to get the right resistance. I would like to shrink it if I run it to the dash or console.

[demick]

I used the 'alternative' circuit, rather than the one with dual switches. So about 250 ohms, and about 2K ohms. I don't believe it's important to get to the exact value - just as long as you are in the ballpark.

[Tool Pants]

You guys are clever. I can just manage to change a light bulb.

Demick asked me to change the air bag coding so that the car thought it has the deactivation bar. But when I looked at his car he did not have it. He said something about using a switch connected to the center console lock.

After I changed the coding he locked it and the air bag warning light started to blink, then stopped. Just as if the deactivation bar was installed.

[geno melici]

this looks like a bad ideal to mess if i did it i would prob set off all the airbags in the car

[martialmedia]

Ha ha. Yeah setting off the airbag might be a violent surprise. I am about to rebuild it with just 2 resistors. I think I will add one of these key switches somewhere rather than just having a box under the seat. http://parts.digikey.com/1/parts/977524-sw...ckm12atw01.html This way it can't get accidentally turned on or off. Now if I can just figure out the best place to put the switch. I will post an update when it is done.

[barge00S]

Anyone know if Durametric can change the Child Seat occupancy setting or does it require a PST2?